Ultra-Rapid Direct Satellite Selection Algorithm for Multi-GNSS

Abstract

GlobalChi, Cheng navigation satellite systems (GNSS) provide many more satellites than ever before. However for applications extremely sensitive toZhan, Xingqun power consumption, notWu, Tong all satellites can be incorporated into the measurement vector, either because of the sheer computation overloadXin, Zhang or for purpose of power saving. These applications include but are not limited to unmanned aerial system (UAS), flying cars, and asset tracking. Thus, satellite selection methodology should be used to obtain subset satellites with good geometry. Recently, a downdate method proposed in receiver autonomous integrity monitoring (RAIM) can be used for reference in satellite selection, although RAIM and GNSS positioning are quite different. In this paper, a DOP-based ultra-rapid satellite selection methodology, the direct satellite selection (DS) method, is proposed according to the downdate method. Furthermore, to compensate for the shortcomings of the DS method, a constrained direct satellite selection (CDS) method is then proposed by adding error monitoring and restrictive conditions. The two algorithms are examined for precision performance and computational performance. Simulations show the DS method performs about three orders of magnitude faster than the recursive method, which is the existing fastest DOP based algorithm, with 0.25 increase in DOP on average relevantly when excluding the number of satellites from 42 to 8. And the CDS method performs about two orders of magnitude faster than the recursive method with only 0.15 increase in DOP even when excluding satellites from 42 to 6. Consequently, both the two methods have much lower computation time than all the existing DOP-based algorithms, with very little reduction in precision. Comparatively, the DS method has lower computational load and the CDS method has higher precision. Thereby, the algorithms proposed in this paper successfully address the satellite selection problem in two scenarios; the CDS method fits in fast satellite selection and high precision situation; the DS method can be employed in some extremely speed demanding circumstances.